Loss of retinal function is a common consequence of aging, but the mechanisms mediating this loss are not fully understood. One possibility is that a reduction in the density of visual pigment or in the regenerative ability of the photoreceptors result in decreased sensitivity or bleaching recovery. The technique of retinal densitometry is used to examine pigment density and pigment regeneration after bleaching for both rods and foveal cones in subjects ranging from 10-70 years of age, and in one subject for whom there is data spanning 25 years. Alterations with age of either pigment density or regeneration measurements will have different implications for understanding aging effects in the photoreceptors or RPE. Comparisons of densitometric measurements with psychophysical dark-adaptation curves obtained under identical conditions will determine the extent to which pigment changes can account for threshold changes with age. The rod and cone densitometric data, and the foveal cone psychophysical data, will provide normative values not currently available for different age groups. To avoid the inconvenience and slight danger of dilating the subject's pupil, the densitometric measurements are made through the natural pupil. Densitometric measurements have been found to be affected by the size of the pupil, however, and that relationship is explored in preliminary experiments.